The Shrieking Shack
This used to be thought the most haunted house in all of Britain, as people claimed to hear shrieks coming from the little house's interior. This, of course, was later found to be the wails of one Remus Lupin as he turned into a werewolf during his school days. This shack was built for the purpose of giving him a place to transform far away from the other students. A passage was created under the Whomping Willow so he could get there from the Hogwarts campus. Should someone prod a particular knot on the Willow's trunk, the passage will open and lead them to the Shrieking Shack.
Now people come here to see the legendary shack.